"The IMF is the only fire-brigade available to the global economy," he said. "It is vital that the IMF has the necessary tools to deal with the current eurozone crisis and the risks to wider global financial stability.

"Any IMF loans to the eurozone must be on rigorous terms, with full conditionality.

"The IMF must not flinch from its long-standing policy of negotiating only with member countries."

The Tory MP added: "Britain benefits more than most from having a tough global watchdog and no country outside the eurozone has more reason to want the crisis resolved than the UK."

"He isn't taken seriously at home and now with this opportunistic approach he isn't taken seriously around the world," she said.

"George Osborne is taking the tough, responsible decisions. It's about time Labour started doing the same."

Camborne and Redruth MP George Eustice said: "Britain should play its part to help stabilise the world economy so we should support the IMF but we must also ensure that the financial help only goes to support countries and that eurozone members take responsibility for their currency."

Writing on his blog, he suggested the loan "makes you wonder how all those earlier bailouts have worked out".

Osborne told BBC Radio 4's Today programme: "When you look at the Tory backbench opinion, of course some people have been critical and they have been critical all along, but actually quite a lot of Conservative backbenchers have come out and said this is the necessary and right thing.

"I think there is a broad body of Conservative opinion that understands we are doing the right thing."